A novel fluidized bed respirometric technique for determination of in situ biofilm kinetics

摘要

A respirometric approach has been developed to determine heterotrophic biofilm kinetics using fluidized bioparticles - particles with attached biomass. Lava rock particles of 600 μm were used as a biomass carrier medium. The modified respirometer successfully estimates in situ biofilm kinetics of the bioparticles collected from a pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor. The observed maximum specific growth rates (μ_(max)) of 3.69 ± 0.44 d~(-1) and biomass yields (Y_11) of 0.36 ± 0.03 g COD/g COD in the fluidized bed respirometers were significantly different from the μ_(max) of 5.57-5.72 d~(-1) and Yh of 0.54-0.59 g COD/g COD observed in the conventional respirometric tests for bioparticles and detached biomass. The higher Monod half-saturation coefficient (Ks) of 186-219 mg COD/L observed in the fluidized bed respirometers relative to the 49-58 mg COD/L in the conventional respirometers reveals the presence of mass transfer resistance in the LSCFB despite fluidization. Significantly reduced yields in the fluidized bed respirometers and the estimated maintenance coefficient of 1.16 d~(-1) for the particulate biofilm in the LSCFB clearly emphasize that a substantial amount of substrate was utilized for cell maintenance at the low food to microorganism (S/X) ratio of 0.5 g COD/g VSS.